Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
Repeated reading of data by a specified number of times from a NAND flash memory or a similar memory causes an error of incorrect reading of data, a so-called read disturb.
In view of this, there is a known method in which a flash memory is refreshed at an every specified timing, for example.
This method refreshes (re-writes) any given number of target blocks among a plurality of blocks constituting the flash memory. Specifically, data is read to a buffer in units of target blocks. Then, the read data are written to another block again.
Accordingly, this method can sequentially refresh the any given number of target blocks in units of blocks.
However, the technique writes the data in the target block to another block again. Therefore, a logic block needs to be made correspond to a physical block or a similar operation is required. As a result, a refresh process is complicated.